Limit stop incremental drive system

ABSTRACT

The authority of known actuators can be made to vary only by halting or disengaging a motor drive to the actuator. The authority of the actuator of the present invention is incrementally variable in small steps. Each operation of a switch produces a predetermined limited movement in the actuator. To achieve large authority levels the switch must be operated a number of times.

United States Patent 72] Inventors Frederick John Pain;

Donald Keerie, both of London, England [21] App]. No. 885,397

[22] Filed Dec. 16, 1969 [45] Patented Oct. 5, 1971 [73] Assignee Elliott Brothers (London) Limited London, England [32] Priority Dec. 18, 1968 [33] Great Britain [54] LIMIT STOP INCREMENTAL DRIVE SYSTEM 8 Claims, 6 Drawing Figs. [52] U.S. Cl 192/142 R, 192/145, 74/84, 74/1 25.5 [51] Int. Cl F16d 71/00 [50] Field of Search 192/482,

[5 6] References Cited UNITED STATES PATENTS 2,023,235 12/1935 Le Count 74/112 2,737,278 3/1956 Bartelt 192/145 2,810,302 10/1957 James et al. 74/112 X Primary Examiner-Allan D. Herrmann Attorney-Misegades & Douglas ABSTRACT: The authority of known actuators can be made to vary only by halting or disengaging a motor drive to the actuator. The authority of the actuator of the present invention is incrementally variable in small steps. Each operation of a switch produces a predetermined limited movement in the actuator. To achieve large authority levels the switch must be operated a number of times.

PATENTED OCT 5 l97l SHEET 1 OF 3 Inventors Frederick John Pain et a1 Misegades and Douglas Attorneys PATENTED mm 5 IHYI 3,610,386

SHEET 2 OF 3 FIG.2

PATENTED nm 5 mm SHEET 3 [IF 3 FIG.3

l 9 6 2 m v m F m m 4 ARE 2 3 m 3 LIMIT STOP INCREMENTAL DRIVE SYSTEM This invention relates to actuators.

It is known to provide an actuator which is movable at a constant rate in one or the other of two opposite directions in dependence upon the sense of rotation of the motor. The limits of authority of the actuator are defined by two stops; movement of the actuator to either of the stops operates switch means in the motor circuit so as, by stopping the motor, to arrest the actuator. To achieve an actuator movement of less than full authority it has been necessary to carefully control the duration of energization of the motor, by the manual closure of a switch in the motor circuit.

In accordance with the invention, there is provided an actuator in which:

a first member is movable, from a datum position, in either of two directions, to a stop limited position, against a spring bias urging the member towards the datum position;

movement of the said first member is effected by way of a first friction clutch;

a second or output member is adapted to be coupled to the first member by a second friction clutch; and

a control arrangement is operable, when in one state, to cause engagement of the clutches so that the output member is able to move to a position determined by the stop limited position of the first member and, when in another state to disengage the clutches so that the first member is able to return, under its spring bias, to its datum.

The authority of the actuator is, accordingly, incrementally variable. With the control arrangement in the said one state the output member of the actuator moves to its stop limited position. After the first member has returned to its datum the control arrangement may be again set to the said one state so as to produce a further movement of the output member. The authority of the actuator therefore increases in predetermined increments the number of such increments being determined by the number of times that the control arrangement is set to the said one state.

The first member may be a rotary member movable in either sense.

According to the invention, also, there is provided an actuator in which:

a first rotary member is movable in either sense from a datum position through a stop limited angle against a spring bias urging the member towards the datum;

rotary movement is imparted to the rotary member by way of a first friction clutch;

a second or output rotary member is adapted to be coupled to the first rotary member by a second friction clutch; and

a control arrangement, which includes an input member manually movable away from and automatically returnable to a neutral position, is operable, when the input member is moved from the neutral position, to cause engagement of the clutches so that the output rotary member is able to rotate through a limited angle determined by the stop limited angle permitted to the first rotary member and, when the input member moves to its neutral position, to cause disengagement of the clutches so as to permit the first rotary member to return, under the bias, to its datum.

The clutches may be electrically actuable, and the control arrangement then comprises electrical circuitry switchable to one state to cause clutch engagement and to another state to cause clutch disengagement.

The input member may comprise a manually operable electric switch biased towards a neutral position; movement of the switch away from the neutral position switches the electrical circuitry to the said one state and movement of the switch, under the bias, to the neutral position, switches the circuitry to the said other state.

The output member may be restrained against movement during disengagement of the clutches.

The output member may include a step-down gearing which opposes movement of the output member during clutch disengagement.

There may be a brake actuatable by the control arrangement so as to engage the output member during clutch disengagement.

The circuitry may be operable when switched to the one state, to energize an electric motor connected to the first friction clutch.

Between the motor and the first friction clutch there may be a step-down gearing.

An actuator in accordance with the invention is hereinafter described with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of a system incorporating an actuator;

FIG. 2 shows, in part section, a practical packaging of the system of FIG. 1;

FIG. 3 is a section on IIIIII of FIG. 2;

FIG. 4 is a schematic diagram of the circuitry employed in the actuation of the system of FIGS. 1 and 2;

FIG. 5 shows on an enlarged scale an end view of a limit and reset mechanism forming part of the actuator of FIGS. 1 and 2; and

FIG. 6 is a section on the line VI-VI of FIG. 5.

The system (FIG. 1 or FIG. 2) comprises an actuator 11, a reversible electric motor 13, a step-down gearing I5, and a step-down gearing 17.

The actuator 11 comprises a first member in the form of a limit and reset mechanism 21, a friction clutch 23, and a fric tion clutch 25.

The mechanism 21, shown in detail in FIGS. 5 and 6, has a flanged rotary shaft 27, the flange 29 of which carries an axially extending peg 31. Surrounding the shaft 27 there is a sleeve 33 having an arm 35; surrounding the sleeve 33 there is a further sleeve 37 having an am 39. A coil spring 41 surrounds the sleeve 37. The ends of the spring 41 are secured to the sleeves 33 and 37. The ends of the arms 35 and 39 contact opposite surfaces of a wall 43 under the bias produced by windup in the spring 41. The peg 31 extends into the space 45 between the arms 35 and 39 with the result that, the shaft 27 is held in a central or datum position. Under clockwise rotation (FIG. 5) of the shaft 27 the arm 35 is moved angularly by the peg 31 until arrested, at clockwise displacement from datum, by a stop 47. Similarly, under counterclockwise rotation of the shaft 27, the arm 39 is angularly moved by the peg 31 until arrested, at 180 counterclockwise displacement from datum, by a stop 49. Movement of the arms 35 and 39 to the stop limited positions 47 and 49, respectively, operates limit microswitches 51 and 53 respectively. The microswitches will be discussed further in relation to FIG. 4.

The shaft 27 is connected by a coupling 55 to the output shaft of the friction clutch 23.

The clutch 23 is an electromagnetic clutch, preferably of the type in which friction members are urged into frictional engagement by the magnetic field produced by energization of an electric winding. The input to the clutch 23 is connected to the reversible motor 13 by the gearing 15.

The flange 29 of the shaft 27 has a recess or cavity which receives an enlarged end 57' of the input shaft 57 of the friction clutch 25. The shaft 57 is fastened to the shaft 27 by a plate 59 secured to the flange 29 by screws, as 61. The clutch 25 is preferably of similar type to clutch 23 that is to say an electromagnetic clutch, preferably of the type in which friction members are urged into frictional engagement by the magnetic field produced by energization of an electric winding. The casing of the clutch 25 also houses a brake 63 which engages the driven friction member of the clutch 25, when the friction members are disengaged, so as to hold the output shaft of the clutch against movement.

The output shaft of the clutch 25 is connected by the stepdown gearing 17 to the input shaft of a further friction clutch The clutches 23 and 25 may be controlled by circuitry as shown in FIG. 4. The latter circuitry has an input member comprising a spring centered, double-pole, double-throw switch 67. Manual movement of the switch armature so as to make with contacts 69 energizes the motor 13 with 28 v. DC by way of the limit switches 51 and 53.

Assume that with the contacts 69 made the motor 13 is energized through microswitches 51 and 53 so that the shaft 27 rotates in a clockwise sense (FIG. 5). When the arm 35 reaches the stop 47 operation of the switch 51 deenergizes the motor 13 and the winding 25 of the clutch 25.

The driven member of the clutch 25 is subjected to the action of the brake 63. The winding 23' of the clutch 23 remains energized, however, until the switch 67 is manually released by the operator, the winding being energized by a circuit which includes diode 71. When the switch 67 is released it centers under its spring bias and the clutch 23 then disengages. With both clutches 23 and 25 disengaged the mechanism 21 is reset under the bias of the spring 41. When arm 35 moves ofi its stop, the associated limit switch, i.e. switch 51, closes preparatory to a further actuation of the switch 67.

in a similar manner, when the switch 67 is operated so that the switch annature makes with contacts 69', the motor 13 is energized and the clutches 23 and 25 are engaged as a result of energization of the windings 23, 25', respectively. When the arm 39 reaches the stop 49 the switch 53 is opened by the arm 39. As a result, the clutch 25 is disengaged. As before, the clutch 23 remains engaged until the switch 67 is released, as a result of energization of the winding 23' by a circuit which includes diode 71.

The limited angular movement of the shaft 27, of the limit and reset mechanism 21, is transmitted to a rotary second or output member comprising the output shaft 66 of the system by way of the step-down gearing 17 and clutch 65. The gearing 17 is such that in response to a 180 movement of the shaft 27 the output shaft 66 executes a 12 movement, say.

The circuit (FIG. 4) also includes a further diode 72 which suppresses transients arising at release of the switch 67. Although a brake 63 is employed to hold the output shaft of the clutch 25, it may be possible, in some circumstances to discard this brake and to rely on the stepdown gearing 17 to act not only to transmit angular motion but also to prevent such motion following disengagement of clutch 25.

We claim:

1. An actuator in which:

a first member is movable, from a datum position, in either of two directions, to a stop limited position, against a spring bias urging the member towards the datum position;

movement of the said first member is effected by way of a first friction clutch;

a second or output member is adapted to be coupled to the first member by a second friction clutch; and

a control arrangement is operable, when in one state, to cause engagement of the clutches so that the output member is able to move to a position determined by the stop limited position of the first member and, when in another state to disengage the clutches so that the first member is able to return, under its spring bias, to its datum.

2. An actuator according to claim 1 in which the first member is a rotary member movable in either sense.

3. An actuator in which:

a first rotary member is movable in either sense from a datum position through a stop limited angle against a spring bias urging the member towards the datum;

rotary movement is imparted to the rotary member by way of a first friction clutch;

a second or output rotary member is adapted to be coupled to the first rotary member by a second friction clutch; and

a control arrangement, which includes an input member manually movable away from and automatically retumable to a neutral position, is operable, when the input member is moved from the neutral position, to cause engagement of the clutches so that the output rotary member 15 able to rotate through a limited angle determined by the stop limited angle permitted to the first rotary member and, when the input member moves to its neutral position, to cause disengagement of the clutches so as to permit the first rotary member to return, under the bias, to its datum.

4. An actuator according to claim 3 in which the clutches are electrically actuable, and the control arrangement comprises electrical circuitry switchable to one state to cause clutch engagement and to another state to cause clutch disengagement.

5. An actuator according to claim 4 in which the input member comprises a manually operable electric switch biased towards a neutral position; movement of the switch away from the neutral position switches the electrical circuitry to the said one state and movement of the switch, under the bias, to the neutral position, switches the circuitry to the said other state.

6. An actuator according to claim 5 in which the output member is restrained against movement during disengagement of the clutches.

7. An actuator according to claim 6 in which the output member includes a step-down gearing which opposes movement of the output member during clutch disengagement.

8. An actuator according to claim 7 in which there is a brake actuable by the control arrangement so as to engage the output member during clutch disengagement. 

1. An actuator in which: a first member is movable, from a datum position, in either of two directions, to a stop limited position, against a spring bias urging the member towards the datum position; movement of the said first member is effected by way of a first friction clutch; a second or output member is adapted to be coupled to the first member by a second friction clutch; and a control arrangement is operable, when in one state, to cause engagement of the clutches so that the output member is able to move to a position determined by the stop limited position of the first member and, when in another state to disengage the clutches so that the first member is able to return, under its spring bias, to its datum.
 2. An actuator according to claim 1 in which the first member is a rotary member movable in either sense.
 3. An actuator in which: a first rotary member is movable in either sense from a datum position through a stop limited angle against a spring bias urging the member towards the datum; rotary movement is imparted to the rotary member by way of a first friction clutch; a second or output rotary member is adapted to be coupled to the first rotary member by a second friction clutch; and a control arrangement, which includes an input member manually movable away from and automatically returnable to a neutral position, is operable, when the input member is moved from the neutral position, to cause engagement of the clutches so that the output rotary member is able to rotate through a limited angle determined by the stop limited angle permitted to the first rotary member and, when the input member moves to its neutral position, to cause disengagement of the clutches so as to permit the first rotary member to return, under the bias, to its datum.
 4. An actuator according to claim 3 in which the clutches are electrically actuable, and the control arrangement comprises electrical circuitry switchable to one state to cause clutch engagement and to another state to cause clutch disengagement.
 5. An actuator according to claim 4 in which the input member comprises a manually operable electric switch biased towards a neutral position; movement of the switch away from the neutral position switches the electrical circuitry to the said one state and movement of the switch, under the bias, to the neutral position, switches the circuitry to the said other state.
 6. An actuator according to claim 5 in which the output member is restrained against movement during disengagement of the clutches.
 7. An actuator according to claim 6 in which the output member includes a step-down gearing which opposes movement of the output member during clutch disengagement.
 8. An actuator according to claim 7 in which there is a brake actuable by the control arrangement so as to engage the output member during clutch disengagement. 